The present invention relates to a semiconductor device, and more particularly, to a semiconductor device with an improved bonding section.
A conventional bonding section formed on a main surface of a semiconductor chip is shown in FIG. 1. An epitaxial layer 2 of N type is formed in a semiconductor substrate 1 of P type. An insulating layer 3 made of SiO.sub.2 approx. 1.0 .mu. thick is formed on the p-type semiconductor substrate 1. On the insulating layer 3 a bonding pad 4 made of aluminum approx 1.0 .mu. thick is formed, and this is further bonded to a bonding wire 5 made of gold. An N-type epitaxial layer 2a under the bonding pad 4 is electrically insulated from the other N-type epitaxial layers 2 by a p.sup.+ -type diffusion region 6 shaped like a ring. The diffusion region 6 is provided for preventing the flow of a leak current which might be generated if the insulating layer 3 were cracked by an impact at the time of bonding.
The conventional semiconductor device thus structured involves the following problems. First, it is impossible to form semiconductor elements, for example, transistors, diodes, resistors, etc., and interconnections, on the N-type epitaxial layer 2a under the bonding pad 4. The reason for this is that, with the impact at the time of bonding, the semiconductor elements may be destroyed or the interconnection may be broken. In particular, when an Al alloy containing Cu is used for the bonding pad, a large urging force is required, resulting in a great impact being delivered to the semiconductor substrate. Since an area of the semiconductor pad is generally 10,000 .mu..sup.2, this leads to an ineffective utilization of the area of the semiconductor chip.
As shown in FIG. 1, the provision of the P.sup.+ -type diffusion region 6 is necessary to electrically insulate the N-type epitaxial layer 2a under the bonding pad 4. The width of the p.sup.+ -type diffusion region 6 must be at least 10 .mu.. The provision of the P.sup.+ -type diffusion region 6 also hinders the miniaturization of the semiconductor devices.
Further, the adverse effects of the bonding upon the semiconductor device during the course of its manufacture extend to semiconductor regions other than those under the bonding pad 4. As a result, the PN junction is damaged, leading to generation of the leak current. The counter-measures conventionally taken to solve this leak current problem are not satisfactory.